We started having trouble with mass mailings at the start of 2018. CiviCRM's tracking did not yield helpful information: mailing reports state 100% of emails were delivered, and I knew this to be inaccurate.
I set up Sendgrid, and for first four months had excellent delivery rates. In May, 14% of our emails were blocked. After a lot of conversations with Sendgrid support, it turns out this is because others on our shared IP have spammy practices.
the price to solve this is to have a dedicated IP at $80/month. This is steep for us, like other many CiviCRM users, we are a very small nonprofit. (also, I resent being extorted. We chose a plan because of how many emails we send; had I been informed that we would receive poor service at that price, I would have made a different choice.)
But looking around, I do not see other email platforms that are as easily compatible with CiviCRM. SendinBlue, for instance, has plugins for CMSs, but not CRMs.
Does anyone have a good experience with a transactional email service? Or suggestions on how to see more accurate tracking from CiviCRM?